GB369799A - Improvements in and relating to colour photography - Google Patents

Abstract

369,799. Colour photography. DU PONT FILM MANUFACTURING CORPORATION, (formerly Du Pont Pathe Film Manufacturing Corporation), 35, West 45th Street, New York, U.S.A. May 27, 1931, No. 15496. Convention date, June 19, 1930. [Class 98 (ii).] A colour filter layer is applied to the surface of an emulsion in the form of a mechanically inseparable coating of transparent material (e.g. gelatin, agar-agar, or casein) containing a dye in a water-insoluble and mordanted state which will not bleed into the emulsion, and can be subsequently removed by chemical or mechanical destruction. In a bi-pack the coating 3 may be applied to the emulsion surface of the blue-green sensitive emulsion 2 which is in contact with the panchromatic or other emulsion 4 of the rear plate or film. Alternatively the layer may be on the rear emulsion 4. In a tri-pack another similar coating may be applied on the back surface of the middle film support or as the emulsion surface of the rear films. For preparing the filter layer Luxol Fast Red B dye may be fixed in a gelatin solution by adding alum. Formaldehyde or other hardening agent may also be added. The mixture is then chilled and set to a jelly, shredded and washed to remove excessive dye. It is then melted and diluted to any desired degree for coating. The colloid coating also forms a better surface contact with the adjacent emulsion and obviates light scattering and diffusion.